Mike Frysinger wrote:
> Most of the macros in msr.h already use __asm__ and __volatile__, this patch
> brings the rest into line. This is needed since these get exported into
> userspace (need to use strict __asm__ vs asm when gcc compiles with GNU
> extensions turned off).
> ---
> diff --git a/include/asm-x86_64/msr.h b/include/asm-x86_64/msr.h
> index d5c55b8..ed15d2b 100644
> --- a/include/asm-x86_64/msr.h
> +++ b/include/asm-x86_64/msr.h
> @@ -33,7 +33,7 @@
>
> /* wrmsr with exception handling */
> #define wrmsr_safe(msr,a,b) ({ int ret__; \
> - asm volatile("2: wrmsr ; xorl %0,%0\n" \
> + __asm__ __volatile__("2: wrmsr ; xorl %0,%0\n" \
> "1:\n\t" \
> ".section .fixup,\"ax\"\n\t" \
> "3: movl %4,%0 ; jmp 1b\n\t" \
> @@ -50,7 +50,7 @@
>
> #define rdmsr_safe(msr,a,b) \
> ({ int ret__; \
> - asm volatile ("1: rdmsr\n" \
> + __asm__ __volatile__ ("1: rdmsr\n" \
> "2:\n" \
> ".section .fixup,\"ax\"\n" \
> "3: movl %4,%0\n" \
NAK.
This is wrong for two reasons:
- MSRs are not accessible in user space.
- .section .fixup is not applicable to user space.
Anything MSR-related should be protected by __KERNEL__ instead.
This NAK doesn't apply to rdtsc* and rdpmc* changes, however, as those
instructions are legitimate in userspace.
-hpa
-
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